The White House-led review will consider whether the government should continue providing such equipment and, if so, whether local authorities have sufficient training to use it appropriately, said senior administration and law enforcement officials. The government will also consider whether it is keeping a close enough watch on equipment inventories, and how the weapons and other gear are used.

The review, coupled with proposed legislation and planned congressional hearings, opens the possibility for significant changes in Washington’s approach to arming local law enforcement agencies. Following the attacks of Sept. 11, 2001, the government regarded the police as the frontline forces in a new war. While that role for local law enforcement is expected to remain, changes may be ordered to the system under which federal grants and a military surplus program have sent gear and money to police departments, often with no strings attached, to prepare for a terrorist attack.

America got a glimpse of that gear over the past two weeks in Ferguson, Mo., as police officers in full body armor rode military-style vehicles, firing tear gas and pointing assault rifles at protesters. Like departments nationwide, the police in the St. Louis area have been outfitted by federal grants and military surplus.

“The whole country and every representative and senator have seen the visuals, and at some level, it made all of us uncomfortable,” said Senator Claire McCaskill, Democrat of Missouri, a member of the Senate Homeland Security and Governmental Affairs Committee who will lead a hearing in September into police use of military-style equipment. “It’s a moment where we can take a timeout and look at these policies.”

Such reviews would have been unlikely in Washington before the Ferguson protests, which followed the shooting death of an unarmed teenager by a police officer. For years, internal audits have raised concerns about the management and oversight of federal grants, but nothing until now has prompted the government to question the wisdom behind the programs.

After the 9/11 attacks, the government pushed billions of dollars to local law enforcement agencies through the Department of Justice and the newly created Department of Homeland Security. The grants paid for radios that allowed local police and fire officials to talk to each other during a crisis. Grants placed lifesaving equipment in ambulances and hospitals.

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Marines under fire in Afghanistan in 2010. Paul Eaton, a retired Army general, said soldiers were taught to keep the barrel no higher than a 45-degree angle.Credit...Tyler Hicks/The New York Times

Attorney General Eric H. Holder Jr., in a statement released by his office on Saturday, said this equipment “flowed to local police forces because they were increasingly being asked to assist in counterterrorism.” But he also said that “displays of force in response to mostly peaceful demonstrations can be counterproductive,” and so “it makes sense to take a look at whether military-style equipment is being acquired for the right purposes and whether there is proper training on when and how to deploy it.”

For police departments, the money has paid for computers, armored vehicles, body armor, weapons, training and more. In Washington, the only debates were whether the George W. Bush administration was providing equipment fast enough, and whether departments were getting their fair shares.

But the rush to arm America’s police departments made oversight difficult. Grant programs overlapped. Money often flowed to state governments first before arriving in local police departments, making it hard to track. In 2009, auditors cited examples of state governments that could not verify what equipment local authorities had bought.

The federal government also did not typically insist that local authorities be trained on how and when to use its new equipment. In recent days, retired military officers have bristled at the sight of police officers in Missouri walking the streets with guns drawn, pointed at protesters.

“In the infantry, we teach ‘muzzle awareness,’ ” said Paul D. Eaton, a retired general who previously served as the Army’s chief of infantry at Fort Benning, Ga. “Their fingers are off the trigger. They are on the trigger guard. The barrel is either straight down or no higher than a 45-degree angle. The effort is to declare a presence, but not to declare you are on the offensive.”

Administration and law enforcement officials said the White House review would include an examination of training requirements.

The review will also look at a program the Obama administration likes. The Edward Byrne Memorial Justice Assistance Grant program is the leading source of Justice Department money to state and local authorities. Vice President Joseph R. Biden Jr. is a longtime supporter of the grants, which can be used to hire police officers, expand drug task forces and buy weapons, armor and other equipment.

Though violent crime is at its lowest level in a generation and terrorism, despite fears and continuing global threats, remains exceedingly rare on American soil, any effort to significantly cut police funding would be met with sharp opposition from local and state officials and many in Congress. Even if the political will to review the policies exists now, it is not clear whether it will remain when lawmakers return from vacation next month and see the midterm elections on the horizon.

Ms. McCaskill agreed that the military equipment had proved valuable. In Ferguson, she said, a BearCat armored truck, paid for with $360,000 in Homeland Security grants, helped the police escape harm amid gunfire. And while she was critical of the police response, she said no police officer had fired lethal weapons on protesters, even when people in the crowd were firing.

Still, Ms. McCaskill said, the government should be able to find a way to ensure officer safety and keep streets safe more strategically. She said one alternative to the current system would be to store military equipment with the National Guard and allow the police to use it only when needed.

The White House review will also include scrutiny of a Pentagon program that transfers surplus military equipment to police departments. Congress created the program in the 1990s as a way to help the police fight drug crime and violence. After 9/11, as the military ramped up to fight two wars, the program grew in the name of fighting terrorism. Lately, police departments big and small have been outfitting themselves with aircraft, night-vision goggles and trucks built to survive buried roadside bombs.

Defense Secretary Chuck Hagel is “keeping an open mind” about the program, said Rear Adm. John F. Kirby, the Pentagon press secretary. “He shares the president’s concerns about any blurring of lines between the military and local law enforcement, of course, certainly, as that concern could lead to the use of military equipment.” Admiral Kirby noted that most of the equipment transferred to local police by the Defense Department did not include weapons or armored vehicles, which are bought through a separate fund.

Representative Hank Johnson, Democrat of Georgia, said he would propose legislation putting limitations on the program, including a requirement that local police certify that they are trained to use the equipment.

The White House review and congressional interest come at a time when many liberal Democrats and libertarian-minded Republicans have joined forces in calling for an end to national security policies that they see as infringing on civil rights. Some of the lawmakers leading the fight against the National Security Agency’s bulk collection of American phone records have spoken out against police departments that look more like the military.

“The images and scenes we continue to see in Ferguson resemble war more than traditional police action,” Senator Rand Paul, a Kentucky Republican and likely presidential candidate, wrote last week in Time.

But Representative Peter T. King, Republican of New York, a member of both the Intelligence and Homeland Security committees, dismissed that criticism and said he had seen nothing to justify scaling back federal police grants. He said there was no evidence that giving the police heavy weaponry and equipment worsened the situation in Ferguson or led to abuses elsewhere.

Mr. King said he disagreed with anyone who might say “that somehow the police are the cause of what’s wrong.”